Ferdinand - '85 Bronco 351W XLT "Phoenix" rebuild project...

[grumpin]

It'll be great when you get it all ironed out!

[Ferdinand]

Thanks for the encouragement guys.

This is really becoming a battle of the will...

SO after talking this thing to death with anyone and everyone I could find in addition to all the wisdom here, I thought we had it figured down to fuel delivery. AND, with the rebuilt carb being one large suspect variable I reached out and found a friend with a known good Edelbrock 500 in a box and we bolted it up and it ran like a dream! (although we didn't do the "under load" test. I thought for sure for how smooth it ran and took throttle stabs, surely it was the carb. So, I pulled the trigger and bought a new one.

Here is the result:

[Gary Lewis]

BUMMER!  

Well, lemme think.  The fact that the 500 "like a dream" suggests that is is the carb.  You didn't do an "under load" test - does that mean you didn't put it in gear or just didn't drive it?

So, you have a brand new carb, and it didn't run as well as the 500.  But, was it better or different than your original carb?

The issue with stumbling on throttle-up may be the accelerator pump adjustment.  Or, the pump may be bad.  I'd play w/the adjustment and, if needed, pull the cover on the carb to see what's inside.

[grumpin]

What about the EGR valve?

Just trying to think of what would make it stumble and/or stall.

[Steve83]

Read this caption, especially the 2nd paragraph under "Overview":



So that means the EGR is normally "off" (regardless if it's controlled by an EEC or by a complicated vacuum system), which means it's safe to temporarily disable it to eliminate it as a possible cause for your idle concerns.  A simple piece of Aluminum foil slipped between the valve & its adapter plate (if yours is built that way) is usually enough to block all flow at idle.

[Ferdinand]

So, in the process of trying to build a very simple straight forward vehicle to have for years to come and since nearly all of the emissions and vacuum related components had melted into large clumps, I have opted for the simplest configuration under the hood I could muster.

No EGR, removed all Thermactor pump pieces and parts, removed head cross tube, etc. Pretty simple. Which is why I feel like I am missing something right in front of my eyes Because there really isn't that much going on.

The only thing my carb is connected to at the moment is the power brake booster and the transmission module. I was told by several "gurus" to not connect my vacuum advance on the distributer yet, though I have had that connected for most of the past videos. It is off now.



I have checked for any vacuum leaks - none. I have metered out my plug wires - all good. I have checked my firing order again - correct.

I pulled temps on my cylinders which is another indicator that something is just not right.
They are as follows:
1 - 709
2 - 590
3 - 190
4 - 131
5 - 152
6 - 650
7 - 194
8 - 505
Now, I have no idea what these should be just yet and I admittedly didn't shoot each temp at the exact location on the header tube, but this seems way wrong to me. I would expect maybe a 50 degree difference AT MOST between cylinders, but maybe I'm wrong. At this point who knows?

I have been told this is likely still a vacuum problem. So, I go back tonight with that in mind. I will trace every living thing in the truck I can think of (most all of which is already disconnected) and pray something turns up. 🙏🏻

[Gary Lewis]

Yes, I'd disconnect EVERYTHING associated with vacuum.  You sure don't need brakes as fast as you are going and you don't the vacuum advance.  Nor heater.  So plug everything.  Inc the line to the tranny.

As for the temps, something is waaaay wrong.  It looks like 3, 4, 5, & 7 aren't running anywhere near correctly.  The firing order is supposed to be: 1-3-7-2-6-5-4-8.  Right?  So could 3 and 7 be swapped?  And 4 and 7?  You've said, repeatedly, that you have the order nailed, but we are grasping at straws, and that looks like a straw to me.

And, have you tried squirting something like brake or carb cleaner at the intake/head gasket?  It may mess up your paint job, but we are grasping, so....

[Gsmblue]

Jumping late here, sorry if this has been mentioned. But what is the fuel pressure to your 1406 carb? They don't like to be run at high pressure, I think ~4.5psi is the recommended but a stock fuel pump could be ~9psi.

Again sorry if this has been mentioned already!

[Gary Lewis]

That's a really good point.  Edelbrock says no more than 6 psi, so I run a regulator set at 5 1/2.  

[grumpin]

Is your carb sitting on a spacer?

Like Gary mentioned use some brake cleaner to look for a leak.

[Gsmblue]

The 1406 on my Bronco 351W is running rich, feels unresponsive sometimes so I have ordered a larger air cleaner and a Holley 12-803 Fuel Pump Fuel Pressure Regulator. I am at 4000ft altitude, so the slightly thinner air may be an issue for me.

Anyhow, definitely check your fuel pressure..

[Ferdinand]

Awesome thoughts guys.

I will look into trying to figure out my fuel pressure but I'm guessing its a good bit over 4-5 psi.

When "checking for vacuum leaks" I used the ether trick. No pickup detected anywhere...

The air gap I have has no provision for EGR. I will plug everything off tonight vacuum wise and if this sucker still dies IT HAS TO BE THE FUEL. (I hope 🙃)

[Ferdinand]

I've said it before and I'll say it again, the EVTM is ridiculously valuable. Thanks a million Gary!

[Ferdinand]

Are these worthy candidates?



Please make a recommendation if you know of a better one/cheaper one.
(Still want something reliable though 😉)

[Ferdinand]

Yes, the plug wires are right. I get what you are thinking Gary on the cylinder temps, but with the wires right, could there be a problem with the ignition module maybe?

I bought a new one but I did get it from Rock Auto. (I didn't buy the cheap one though)

You know, I just realized I bought an extra. I am going to pop that sucker on tonight to try as well.

[Gary Lewis]

No, I don't think it can be the ignition module as it doesn't know which cylinder it is firing.  But it won't hurt to swap it.

On the fuel pressure regulator, that looks like the one I have and it works well.  But, I don't let anything with a Mr. Gasket brand into my shop, much less onto my truck as I've had some really, REALLY awful parts from them.  So look for another brand, but one that looks like that is what I have.

[Ferdinand]

good call. Yes, I usually avoid Mr. Gasket as well.

[Gary Lewis]

Yep, that should do it.

[Rembrant]

Ferdinand wrote

I pulled temps on my cylinders which is another indicator that something is just not right.
They are as follows:
1 - 709
2 - 590
3 - 190
4 - 131
5 - 152
6 - 650
7 - 194
8 - 505
Now, I have no idea what these should be just yet and I admittedly didn't shoot each temp at the exact location on the header tube, but this seems way wrong to me. I would expect maybe a 50 degree difference AT MOST between cylinders, but maybe I'm wrong. At this point who knows?

Ferdinand,

Were you measuring the temperature on each header tube pretty close to the cylinder head?

I just went and watched a couple videos of when my 302 was on the dyno last spring, and the exhaust temps at idle were pretty even in the 900-1000 degree range. It's hard to see exactly because I wasn't specifically recording the temps, but I'd say they were in the 950 degree range, plus or minus 50 degrees. On the actual dyno pulls to 5500 RPM, the exhaust temps were up in the area of 1350, maybe 1400 degrees, with some big variances...as much as 150 degrees I would say. I think that's just the nature of carburetors and how they work with the intakes.

The engine was pretty well tuned by that point, I think with the AFR in the 13.5 range. I'm not 100% sure, and I'm not at home to dig out my paperwork.

Now...on your actual measurements. It looks like you've got a few cylinders not firing. I feel like I'm the guy that always brings bad news, but have you by chance done a compression check? Couple cam lobes washed out during break-in?....this is a flat tappet engine, right? That does happen.

Feel free to tell me off...I'm not suggesting that you did anything wrong, but for how long it takes to check the compression, it might not hurt to check it. Even if it wasn't a washed out lobe, maybe it would show a mechanical timing issue?...

Just thinking out loud...and I may have missed some info along the way.

[Ferdinand]

Rembrant,

I think you might be on to something there...

I am pulling a compression check tomorrow night. As much as I would hate for that to have happened, it sure would explain a lot!

Did plenty of testing tonight and shot some video, but I will have to upload tomorrow. Getting too late and my laptop is at 4% and I left my charger at my office 🙃